It's a fairly trivial 'desert island cars' kinda question, granted. But I don't necessarily think the answer is trivial, for reasons I'll come back to.
In the meantime, though, as I imagine it, you'd have access to any car from one car maker, from today's range or from any point in its history. And as time goes on, you can drive whatever new models it introduces. The model you wanted to drive would just be there whenever you wanted to drive somewhere, free, fuelled, and in perfect factory condition.
I'm thinking road cars, btw, not racing cars, although homologation specials would be OK.
So who's it to be?
I don't think the list of contenders would be a very lengthy one. Wonderful though the idea of driving some sports cars is, what about when you wanted to go to the tip? What happens if you get sciatica as a dotard? Bravo if you think you can drive only a Caterham between now and the day you croak, but I'm not taking the cat to the vet's in one.
A Porsche, though, I suspect one could quite easily manage. I suppose you'd have to really like 911s, but it's mostly all there in the historic or current range: supercars, sports cars, convertibles, family wagons, 4x4s.
Which leaves, in my mind, two others: Ford and Toyota. Toyota nails practicality and ruggedness, might seem a bit light on the supercar front but there was the GT One roadgoing Le Mans car, the 2000 GT is achingly lovely and it has had some belting small sports cars over time.
Ford has no fewer than two roadgoing Le Mans cars, another pastiche of one and all the ruggedness and practicality you could want, too. It has Mustangs, the impossibly good Racing Puma, and what I think is colloquially known as 'a shit ton' of wicked rally and touring car derived specials. It might not have ever made anything as plush as Mercedes, but you'd never be bored, which I suppose is part of the appeal.
Today I'm erring towards Mercedes-Benz, with Toyota a close second. But tomorrow those could quite easily be reversed. And the day after it could quite easily be somebody else.
[Images: Karissa Hosek, Patrick Ernzen and Darin Schnabel for RM Auctions]